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Electronic structure and optical properties of complex hydrides LiBH4 and NaAlH4 compounds
Author(s) -
Ghellab Torkia,
Charifi Zoulikha,
Baaziz Hakim,
Bouferrache Karim,
Hamad Bothina
Publication year - 2019
Publication title -
international journal of energy research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.808
H-Index - 95
eISSN - 1099-114X
pISSN - 0363-907X
DOI - 10.1002/er.4517
Subject(s) - chemistry , ionic bonding , lithium (medication) , atomic orbital , phase (matter) , covalent bond , hydrogen storage , ion , hydrogen , crystallography , analytical chemistry (journal) , organic chemistry , medicine , physics , quantum mechanics , endocrinology , electron
Summary The properties of the complex hydrides LiBH 4 and NaAlH 4 such as structural, electronic, and optical properties were calculated using the augmented plane wave plus local orbitals (APW + lo) method. The three phases α , β , and γ of LiBH 4 and NaAlH 4 hydrides are studied, the β ‐phase is transformed at the high‐pressure to γ phase for the compound LiBH 4 with the generalized gradient approximation (GGA) with a 16% volume decrease. However, NaAlH 4 compound did not show any phase transition. The interaction between the boron (aluminum) atoms and the hydrogen atoms in the [AlH 4 ] − ( [BH 4 ] − ) complexes is strongly covalent, and between the complexes [AlH 4 ] − and the lithium Li + cations for the LiBH 4 compound and between the complexes [AlH 4 ] − and the sodium Na + cations for the NaAlH 4 compound, the bond is ionic. For the most stable phases of the two complex hydrides, different optical parameters have been calculated as a function of the photon energy. The plasma frequency ω p is calculated from the mean peak of the energy loss function. Therefore, by way of example, the plasma energy ħω p of its peak position is 13.23 (12.93) eV for α‐ NaAlH 4 ( α‐ LiBH 4 ).